Active wireless tag and auxiliary device for use with monitoring center for tracking individuals or objects

ABSTRACT

The invention is directed to a location tracking device and auxiliary device for use with a monitoring center for tracking individuals or objects. The location tracking device has position determining circuitry and first wireless circuitry that communicates position data representative of the location of the tracking device to a remote location (e.g., a monitoring station). The tracking device also has second wireless circuitry that communicates with the auxiliary device. The tracking device has at least two operational modes. The tracking device switches operational modes when communication is established between the tracking device and the auxiliary device. The auxiliary device generally has an associated auxiliary device ID and wireless circuitry that communicates the auxiliary device ID to the location tracking device. The tracking device has a first operational mode, when communication is not established with the auxiliary device, wherein the position determining circuitry is maintained in a normal power state. The tracking device can also have a second operational mode, when communication is established between the tracking device and the auxiliary device. In the second operational mode, the second wireless circuitry receives the auxiliary device ID from the auxiliary device and the first wireless circuitry communicates the auxiliary device ID to the remote location. The tracking device can also have a third operational mode, when communication is established between the tracking device and the auxiliary device. In the third operational mode, the position determining circuitry is placed in a reduced power state.

FIELD OF THE INVENTION

The present invention relates to systems which provide location trackingand monitoring of a portable tracking device or “tag” that is affixed toan individual or other object, and in which the device periodicallycommunicates data to a remote monitoring station. More specifically, thepresent invention relates to the implementation of limited RF capabilityin the tag and another system device, hereinafter “auxiliary device” toprovide improved system features and functions.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority of U.S. Provisional PatentApplication Ser. No. 60/840,844, filed Aug. 29, 2006, and U.S.Provisional Patent Application Ser. No., filed 60/859,232, Nov. 15,2006, the entire contents of which are incorporated herein by reference.This application is also related to concurrently filed U.S. patentapplication Ser. No. ______ entitled “Wireless Tag and Auxiliary Devicefor Use With Home Monitoring Unit for Tracking Individuals or Objects.”

BACKGROUND OF THE INVENTION

Electronic location monitoring and tracking of individuals or objectscan be carried out in a number of ways. Determining the location of thetag can be provided using well-known techniques, such as GPS, cellulartriangulation, or a combination of both. Further, in certain systemapplications, tamper detection capability and the ability to generatealarms upon detecting tampering or upon other conditions may beincluded. There are variants of electronic location monitoring andtracking systems. For example, some systems rely upon electronicmonitoring at a fixed located such as the individual's home or place ofemployment. These systems can rely upon a land line telephone link andare commonly known as house arrest systems. These systems utilize atransmitter worn by the individual and a stationary receiver located atthe monitoring location. When the individual is an “offender”, i.e., aperson under a government-supervised program, the transmitterincorporates tamper-detection capabilities and upon such detection maytransmit an alarm. The worn transmitter transmits a signal a shortdistance to the receiver located at the monitoring location. Thereceiver communicates with a central monitoring service over standardtelephone lines. The tracking system of this type is limited in that itcan only provide an indication of the presence or absence of theindividual at the monitored location at a given time. This type ofsystem cannot offer location information if the individual leaves themonitored location.

U.S. Pat. Nos. 5,867,103 and 6,160,481, which are incorporated byreference herein, disclose a system which provides for a locationaltracking of a plurality of monitored persons. The system has a portablemonitoring device for each of the monitored persons. Each portablemonitoring device has means to secure the device to a respectivemonitored person and may include means to detect tampering with thesecured device for offender applications. Additionally, each portablemonitoring device has means to receive a distinct signal generated by adetached sending unit. Each portable monitoring device also has means totransmit a signal containing data. The system further has means toacquire the signal containing data transmitted by each respectiveportable monitoring device. The system has means to determine apositional location of the portable monitoring device based, at least inpart, upon the distinct signal received by the portable monitoringdevice. The system has means to mark, at least within a range of timereferences, when the positional location reference was determined in theform of an occurrence reference. The system has means to store, forarchival retention within a locational tracking database, at least aseries of the position references and associative occurrence referencesof each portable monitoring devices of the tracking system.

U.S. Pat. No. 6,774,797, which is incorporated by reference herein,discloses a one-piece lightweight waterproof personal tracking tag whichis attached to an individual using either a tamper detection strap orother suitable means of connection. The tag communicates with a globalpositioning satellite network and a wireless network to obtaingeographic location information and to exchange data with a centralizeddata system. The tag monitors the location of the wearer of the tag,compares the monitored location to a database of acceptable andunacceptable location and time parameters and provides updates to acentralized database system, the monitoring center, and receivesdownloads and updates from the system.

For locational tracking and monitoring of one or more individuals, eachhaving an individual set of allowed geographic and temporalrestrictions, the system must maintain an extensive database ofindividuals and corresponding restrictions. In such applications, thetag preferably incorporates a microcontroller, flash memory, a cellularmodem, a GPS receiver, tamper detection, and a rechargeable battery in asingle lightweight unit. One or more individuals are provided with atracking tag. Each of the tags reports into the monitoring center on aperiodic basis. The reporting basis can be on a predetermined scheduleand/or can be based upon detection of a violation or other reportablecondition detected by the tag itself. Information reporting by thevarious tags is recorded and analyzed at the monitoring center by thedata tracking system to determine if individual violations haveoccurred. The centralized data tracking system can then take anappropriate action to notify, respond to and/or correct the notedviolation.

The tag's ability to properly function is limited by the capabilities ofthe tag's battery and the ability of the tag's circuitry to functionproperly in different locations. Current GPS based tracking systems, forexample, will not function properly when GPS reception becomes impairedor is lost. In addition, the demands of system applications placeincreasing power loads and operating time requirements on the tag'sbatteries. Both of these shortcomings can be especially acute inoffender tracking and monitoring applications where loss of offenderlocational monitoring is unacceptable. It would be desirable to providea mechanism for efficiently extending the range of such GPS trackingsystems particularly in areas in which GPS reception is impaired. Itwould also be desirable to provide such extended coverage where noaction is required by the offender. It would also be desirable toprovide such expanded coverage where removal of the offender's GPSdevice is not required.

SUMMARY OF THE INVENTION

The invention is directed to a location tracking device and auxiliarydevice for use with a monitoring center for tracking individuals orobjects. The location tracking device has position determining circuitryand first wireless circuitry that communicates position datarepresentative of the location of the tracking device to a remotelocation (e.g., a monitoring station). The tracking device also hassecond wireless circuitry that communicates with the auxiliary device.The tracking device has at least two operational modes. The trackingdevice switches operational modes when communication is establishedbetween the tracking device and the auxiliary device. The trackingdevice can switch modes automatically once communication is establishedbetween the tracking device and the auxiliary device. In thealternative, the monitoring station can direct the tracking device toswitch operational modes based. The decision on whether to switchoperation modes can be at least partially based on the receivedauxiliary device ID (e.g., the monitoring station can create aninclusion zone as discussed below).

As discussed above, the auxiliary device generally has an associatedauxiliary device ID and wireless circuitry that communicates theauxiliary device ID to the location tracking device. The auxiliarydevice can also include a housing and tamper detection circuitry thatdetects unauthorized movement or opening of the auxiliary device. Theauxiliary can be AC or battery powered and can be portable or can beplaced in a user selectable location. This location can be known to themonitoring station and can be utilized to create an inclusion zone. Inthe alternative, the location of the auxiliary device can be unknown(e.g., portable auxiliary device). In this case, the location of theauxiliary device is effectively determined once communications isestablished with a tracking device (e.g., the tracking device can reportits location and the auxiliary device ID to the monitoring station).This can allow the monitoring station to create an exclusion zone asdiscussed below.

The tracking device has a first operational mode, when communication isnot established with the auxiliary device, wherein the positiondetermining circuitry is maintained in a normal power state. Thetracking device can also have a second operational mode, whencommunication is established between the tracking device and theauxiliary device. In the second operational mode, the second wirelesscircuitry receives the auxiliary device ID from the auxiliary device andthe first wireless circuitry communicates the auxiliary device ID to theremote location. This mode can be used to create an exclusion zone. Thedecision to create an exclusion zone can be at least partially based onthe received auxiliary device ID. In a typical embodiment, the firstwireless circuitry comprises a cellular modem and the second wirelesscircuitry comprises an RF transceiver.

The tracking device can also have a third operational mode, whencommunication is established between the tracking device and theauxiliary device. In the third operational mode, the positiondetermining circuitry is placed in a reduced power state. The secondwireless circuitry receives the auxiliary device ID from the auxiliarydevice and the first wireless circuitry communicates the auxiliarydevice ID to the remote location. This mode can be used to create aninclusion zone. The decision to create an inclusion zone can be at leastpartially based on the received auxiliary device ID. The tracking devicecan also include a battery for powering circuitry associated with, orinternal to, the tracking device. Battery consumption is reduced whenthe position determining circuitry is placed in a reduced power state.The tracking device can also include a housing and a strap that securesthe tracking device to an object or individual and tamper detectioncircuitry that detects unauthorized removal or opening of the trackingdevice.

The tracking device can include signal strength circuitry associatedwith the second wireless circuitry. This signal strength circuitry canbe used by the tracking device to determine whether radio energyreceived by the second wireless circuitry is below a predeterminedthreshold. This can provide range adjustment capability for the secondwireless link. The tracking device can also include i) time slotallocation circuitry and/or ii) frequency allocation circuitry. Thiscircuitry can allow the tracking device to minimize contention forfrequencies or time slots associated with the second wireless circuitry.

The invention is also directed to a location tracking system thatincludes the tracking device and auxiliary device as discussed above.The system can also include a home monitoring unit (HMU) with thirdwireless circuitry that communicates with the auxiliary device wirelesscircuitry and/or the tracking device second wireless circuitry. This canexpand the range of the HMU when communication is established betweenthe location tracking device and the auxiliary device.

In some case the monitoring station can perform i) proximity detectionand/or ii) predictive correlation based on the location of the trackingdevice and the auxiliary device ID.

The invention is also directed to a location tracking method. The methodincludes providing a tracking device having position determiningcircuitry and first wireless circuitry that communicates position datarepresentative of the location of the device to a remote location andsecond wireless circuitry. The method also includes providing anauxiliary device having wireless circuitry that communicates with thetracking device second wireless circuitry. The tracking device has atleast two operational modes. The tracking device switches operationalmodes when communication is established between the location trackingdevice and the auxiliary device as discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, reference is madeto the following description and accompanying drawings:

FIG. 1 shows a block diagram of a system in accordance with theinvention;

FIG. 2 is a block diagram of a tracking tag in accordance with theinvention;

FIG. 3 shows a block diagram of an auxiliary device in accordance withthe invention; and

FIG. 4 shows a block diagram of an exemplary HMU range expansionscenario in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a block diagram of a system in accordance with theinvention. The system includes a central monitoring system (CMS) 10, atracking tag 20 operable to communicate with a Global PositioningSatellite (GPS) network 30 and one or more auxiliary devices 40. Thestrap or tag may incorporate tamper detection using a variety ofwell-know technologies. The tag 20 can be attached to an object orindividual using a strap or other suitable means of connection. Forexample, the tag can be attached to a package that is being transportedfrom one location to another. In the alternative, the tag can beattached to in individual under “house arrest” that being monitored forcompliance. Numerous other scenarios can be envisioned without departingfrom the scope of the invention.

The tag 20 communicates with the GPS network 30 and a wireless network25 to respectively obtain geographic location information and toexchange data with the CMS 10. The CMS monitors the location of the tag(as well as the object or individual to which the tag is attached) andcompares the monitored location to a database of acceptable andunacceptable location and time parameters. The tag generally transmitsposition updates to the CMS and also receives downloads and updates fromthe CMS.

In order to track one or more individuals or objects, each of whichhaving an individual set of allowed geographic and temporalrestrictions, the CMS 10 maintains a database 15 of individuals orobjects and corresponding restrictions. In one embodiment, the tag 20generally incorporates a microcontroller, flash memory, a cellularmodem, a GPS receiver, tamper detection, and a rechargeable battery intoa single unit as discussed in more detail below. While the foregoingdescription focuses primarily on tracking of individuals, it isunderstood that the invention is equally applicable to the tracking ofobjects as well.

In system applications where the location of a plurality of individualsare being monitored and tracked, each such individual is provided with atracking tag. To lengthen battery life and reduce data accumulation,each of the tags preferably reports into the CMS 10 on an intermittentor periodic basis. The reporting basis can be on a predeterminedschedule and/or can be based upon detection of a violation or otherreportable condition detected by the tag itself. Information reportingby the various tags is recorded and analyzed at the CMS to determine ifindividual violations have occurred. The CMS can then take anappropriate action to notify, respond to and/or correct the notedviolation.

The system also includes at least one auxiliary device 40. The auxiliarydevice 40 works in conjunction with the tag 20 which will intermittentlyor periodically request the presence of an auxiliary device 40 bysending out a RF transmission (“ping”) and waiting for a reply from anyauxiliary device in range via the short range radio (or RF) link 45. Thetypical range in an exemplary system is approximately 100 meters in openarea. The auxiliary device includes: power supply circuitry (e.g., forAC or DC power), battery charging circuitry, a battery backup for remoteoperations, a RF transceiver, a microcontroller and various alarmfeatures to detect and report movement, power loss and light ingress asdiscussed in more detail below. Each auxiliary device can be identifiedby a unique serial number which is transmitted in its response to a pingfrom tag 20. The auxiliary device serial number can also be transmittedin a last reported alarm status response. The auxiliary device 40 canstore any alarms in non volatile memory to ensure that in the event ofloss of power data is retained. The auxiliary device can also retain thestatus of any alarms until it is able to reply to a valid request fromtag 20.

I—Tracking Tag

FIG. 2 is a block diagram of a tag 20 in accordance with the invention.The tag 20 has a microcontroller 102, associated flash memory 104 and aGPS receiver 106 which provides up GPS position information to themicrocontroller 102. The tag can include a cellular modem 108 with anassociated SIM card 110 provided for data communication between the tag20 and the CMS 10. As shown in FIG. 1, the tag 20 communicates through awireless network 25 with the CMS 10. A tag configured to communicatewith the CMS via the a cellular network is referred to herein as an“active” tag. The tag 20 also communicates with one or more GPSsatellites in the GPS network 30. The tag 20 also includes an RFtransceiver 150 for communication between the tag and the auxiliarydevice 40 via the RF link 45. This RF link creates an electronic tetherbetween the tag and the auxiliary device. Suitable short range wirelessintegrated circuits and networking firmware for use in accordance withthe invention are available from a variety of sources including MicrelInc., of San Jose, Calif. (www.micrel.com). Communication via the RFlink 45 is discussed in more detail in the following section.

The tag can obtain position information either through the GPS network30 and/or through position determination techniques utilized in thewireless network 25. Wireless (cellular) based techniques for geographiclocation determination, commonly referred to in the wireless industry asgeolocation, can include triangulation, and estimated time of delivery(EOTD) based upon the cellular ID of the base stations from which asignal is received. It is understood that the system can utilizeposition information obtained from GPS or geolocation techniques or bothas needed (e.g., to maximize the coverage area, power utilization and/oraccuracy).

The tag also includes a battery 112 to power the microcontroller 102,the cellular modem 108, the GPS receiver 106 and the other componentswithin the tag 20. The battery 112 resides within the unit in a sealedcompartment and is not removed for recharging so as to avoid potentialleaks which could result from removal and replacement of the battery.Because the unit must be worn by an individual at all times, the tagwill be subjected to water in such environments as showering. Thebattery 112 is recharged while it remains within the tag 20 by means ofcharger 113.

The tag may also include a tamper detection mechanism 114 to avoidunauthorized removal or opening of the tag. The specific tamperdetection mechanism can be implemented in a variety of ways including:i) signal continuity detection, ii) electrical, optical or electromagnetswitches or detectors that detect unauthorized opening of the tag and/oriii) electrical, thermal proximity devices which monitor the proximityof the tag to the individual or object. Accelerometer 115 is alsoprovided and can be used to monitor acceleration of the tag 20. Themicrocontroller 102 can be programmed to generate an alarm based onacceleration beyond a threshold or the like.

The microcontroller 102 controls the operation of the tag 20. Regularpoles of the cellular modem 108 and GPS receiver 106 are carried out tomonitor for incoming command messages and to monitoring the location ofthe tag. The parameters of the monitoring to be performed are programmedinto the microcontroller 102 to respond to variations in the location ofthe tag and to respond to commands received from the CMS 10 through thecellular modem 108.

The flash memory 104 holds the programmed code for the operation of thetag 20. The code is downloaded to the unit utilizing a serial link andcan be modified and/or downloaded through the cellular modem connection108. In the alternative, the code can be downloaded via programming port124.

Communication between the tag 20 and the CMS 10 is carried out via thecellular modem 108. During operation, the modem remains logged into thecellular network, allowing the tag to be called from the CMS to requestcurrent operating status. The tag can also be polled by the CMS todownload the position of the tag as measured by the GPS system and/or todownload other operating parameters such as violation history, positionhistory and/or battery status.

The microcontroller 102 is programmed to monitor for alarm conditions,such as violations of restrictions by the tag wearer. In the event thatan alarm condition occurs, for example low battery voltage, a tamperdetection by the tamper prevention unit 114 or a violation of thegeographic limitations set for the wearer of the tag, themicrocontroller communicates an alarm condition to the CMS 10. Themicrocontroller can run continuously or can be programmed to cycle theentire tag through an intermittent power pattern, such as a sleep mode,to conserve battery power.

The microcontroller code also includes the ability to be manually placedinto a sleep mode wherein the unit is not powered down but onlyinactive, upon receipt of an appropriate command from the CMS 10.Powering down of the tag 20 can be used to prolong the life of thebattery 112. By allowing a power down to be controlled by the CMS, thetag can be powered down without the knowledge of the offender. Becausethe individual does not know when the unit is inactive, the individualcannot take advantage of inactivity to commit an offense withoutdetection. The unit can reactivate after a set period of time, afterbeing connected to a recharger or after receipt of a command toreactivate.

The SIM card 110 is sealed within the tag unit and cannot be accessed bythe wearer. The SIM card contains details relating to cellularactivation and/or the cellular service provider. The term “SIM card” isused herein a general sense and encompasses other devices for use withvarious types of cellular service such as a Universal Integrated CircuitCard (UICC), Removable User Identity Module (RUIM) or the like. The GPSmodule is used with an appropriate antenna 116, such as a patch antennamounted internal to the tag case. The GPS module can also include abattery backup 130 to maintain settings when main power is removed fromthe GPS module. The GPS module when activated will obtain the currentposition of the tag. If no fix is obtained, the tag will report that nofix was obtained. To minimize the power consumption and thereforemaximize the battery charge life, the GPS receiver is used in the pushto fix mode. The receiver is normally asleep and, only when requested,wakes to obtain the current position of the tag.

The tag 20 also collects cell ID from the wireless system through thewireless cellular modem 108 and EOTD information when provided by thenetwork. The use of cell ID and EOTD can be used to determine the tagposition, as is known in the art, however with less accuracy than theGPS receiver. The tag 20 can use this secondary position information asa confirmation of the fix obtained by the GPS receiver or as asubstitute for the GPS positioning when a GPS position is unavailable.

The tag 20 can include an audible alarm such as a buzzer 118, a tactilealarm such as a vibrator 120 to provide an indication to the wearer thata condition requiring attention has been detected. The tag can alsoinclude a panic button 122 to allow the wearer to alert the CMS 10 thata situation requiring attention exists. This button can be particularlyuseful when the tag is used by an individual being monitored because ofthe individuals potential need for assistance. Other visual alerts suchas Tricolor LED 126 (e.g., for system status and the like) and TamperLED 128 can be provided.

II—Auxiliary Device

FIG. 3 shows a block diagram of an auxiliary device 40 in accordancewith the invention. The auxiliary device 40 has a microcontroller 202with associated internal memory and an RF transceiver 250 forcommunication between the tag 20 and the auxiliary device 40 via the RFlink 45. It is understood that the microcontroller 202 can utilizeinternal memory, external memory or both. The auxiliary device alsoincludes a battery 212 to power the microcontroller 202, RF transceiver250 and the other components within the auxiliary device. The battery212 is recharged by means of charger 213. The programming code formicrocontroller 202 can be downloaded via typical techniques. Forexample, the programming for microcontroller 202 can be burned into theappropriate memory device prior to or during assembly. In thealternative, programming code can be downloaded via optional programmingport 224.

The auxiliary device can optionally include a tamper detection mechanism214 to avoid unauthorized removal or opening of the auxiliary device. Anaccelerometer 215 can optionally be provided and can be used to monitormovement of the auxiliary device. The microcontroller 202 can beprogrammed to generate an alarm based on acceleration beyond a thresholdor the like. The auxiliary device 40 may also include an audible alarmsuch as a buzzer 218 to provide an indication that a condition requiringattention has been detected. The auxiliary device is preferableconstructed with a small housing (e.g., 120 mm*80 mm*55 mm) and can beattached to AC power via a suitable cable or adapter (e.g., 12Vadapter). The auxiliary device can be designed to be hard mounted viascrews or other suitable fasteners. In the alternative the auxiliarydevice can be temporarily placed in a location or even worn or carriedby an individual (e.g., operating via battery power). For example, theauxiliary device can be integrated into or attached to an article ofclothing such as shoes, socks, pants, shirts, or jackets. In thealternative, the auxiliary device can be integrated into or attached toa backpack, purse, wallet or other convenient portable accessory.

In operation, the tag 20 will periodically poll (e.g., ping) for thepresence of an auxiliary device 40 via the RF link 45. If an auxiliarydevice is detected (i.e., the auxiliary device responds to the ping) andcommunications can be established with the auxiliary device, theoperational parameters of the tag and/or the system can be altered. Theauxiliary device 40 will typically reply to a tag 20 with some or all ofthe following information: auxiliary device ID, tag ID, status of theauxiliary device (tamper, motion or power). This information is thentransmitted to the CMS 10 by the tag 20. It understood that a variety ofcommunications protocols are suitable for use in accordance with theinvention. It is also understood that in some embodiments,communications between the tag and the auxiliary device can be initiatedby the auxiliary device.

Several modes of operation are discussed in detail below. In each ofthese examples, the tag 20 relays messages from the auxiliary device tothe CMS 10 via cellular modem 108 and wireless network 25. Thisconfiguration is advantageous in that the auxiliary device does notrequire a cellular modem to communicate to the CMS. This results inconsiderable cost savings and minimizes power utilization.

III—Inclusion Zone Operation (GPS Power Down)

In this mode of operation, the location of the auxiliary device 40 isfixed and is known to the CMS 10 (e.g., the location of the auxiliarydevice is stored in the CMS database 15). The system is operable toestablish an inclusion zone defined by the range of the auxiliarydevice. In this mode, so long as the tag 20 is in communication with theauxiliary device, the CMS knows the location of the tag 20. Operation inthis mode proceeds as follows: the tag 20 detects an auxiliary device(i.e., the auxiliary device responds to a ping). The tag establishescommunications with the auxiliary device, and reports some or all of thefollowing information to the CMS 10: auxiliary device ID, tag ID, Statusof the tag (tamper, low battery and charging), status of the auxiliarydevice (tamper, motion or power). The auxiliary device can also beconfigured to recognize one or more auxiliary device groups (e.g., 40,40′, 40″, 40′″) and then alter its operating mode subject to a receiptfrom the auxiliary device that it has no alarms pending.

As an additional precaution, software in the tag 20 or the CMS mayrequire a valid GPS fix before entering a reduced power state. The tag20 will contact the CMS 10 via the cellular modem 108 to confirm it isgoing to into a reduced power or sleep state (i.e., GPS receiver 106 canbe at least partially powered down in order to save battery power). Incases where the tag is unable to contact the CMS, the tag can maintainlist of approved auxiliary devices and the tag can make thedetermination on whether or not to enter a reduced power state. Thislist of approved auxiliary devices can be updated by the CMS as needed.This reduced power state is particularly advantageous in locations whereGPS reception is impaired. If the tag 20 cannot calculate its positionvia GPS, call in to the CMS 10 or if the tag receives an alarm statusfrom the auxiliary device 40, it will remain in normal operating modeand will continue to log its status. It is understood that the locationof the auxiliary device 40 can be fixed after the auxiliary device ispowered up in a given location. Upon the initial communication betweenthe tag and the CMS, the system can enter the location of the auxiliarydevice 40 into the database 15 before allowing the tag to enter a lowpower mode.

During low power mode, the tag 20 will continue to check for tampers onboth itself and the auxiliary device 40. Also during low power mode, thetag 20 can increase its ping rate to the auxiliary device 40 to ensureit remains in range. The ping rate can be set to a random period betweentwo time ranges to minimize contention with other RF devices. The tag 20can receive a response from any member of its associated auxiliarydevice group and will remain asleep. During this mode, the tag 20 canalso be configured to wake up at pre-set intervals to refresh its GPSposition and therefore update its empheris and almanac from any GPSsatellites in view. This ensures that when the tag 20 finally leavesrange of an auxiliary device 40, it is able to quickly obtain a GPSposition. The tag 20 can also be configured to dial into the CMS 10 atthis point and report its status without the need to obtain a new GPSposition or make a successful GSM call before going back to low powermode.

Upon notification from an auxiliary device of any alarm (e.g., powerloss, movement or tamper, lack of valid pings . . . ) the tag 20 willwake up and resume normal mode. The tag 20 will immediately call intothe CMS. 10, download its status and that of the auxiliary device.

IV—Report Only Mode—Exclusion Zone Operation

In this mode of operation, the location of the auxiliary device 40 neednot be known to the CMS 10. Further, for this mode of operation, theauxiliary device may be configured as a portable device that is batteryoperated. This can be provided by an integral auxiliary device or byconfiguring the auxiliary device to have a fixed component and aremovable component respectively analogous to a notebook computer andits “docking station”. Operation in this mode proceeds as follows: thetag 20 detects an auxiliary device (i.e., the auxiliary device respondsto the ping). The tag establishes communications with the auxiliarydevice, and reports some or all of the following information to the CMS10: auxiliary device ID, tag ID, Status of the tag (tamper, low batteryand charging), Status of the auxiliary device (tamper, motion or power).During this mode the tag 20 will continue with its normal operations andlogging but with the additional details of the auxiliary device IDreceived and its status. This logging can occur relatively frequently(e.g., every one minute). During this mode the tag 20 will notify thecentral monitoring system of every auxiliary device heard; the tag 20does not need to be configured with the auxiliary device details. Thismode is advantageous in that the system can establish exclusion zones.That is, once the tag 20 reports the presence of an auxiliary device inan excluded area, the CMS 10 can identify that unauthorized entry intothat zone has taken place. This mode is also applicable to a dualtracking scenario such as the type disclosed in U.S. Pat. No. 5,867,103,which is again incorporated by reference herein.

V—HMU Range Expansion

One or more auxiliary devices can also be used to extend the range of aHome Monitoring Unit (HMU) when used in a traditional “house arrest”situation. This is shown graphically in FIG. 4. In general, the HMU 300communicates with the CMS 10 via communication link 302 (typically aland line telephone link to the PSTN). In this scenario, the HMU is alsoprovided with an RF receiver that is operable to monitor the RF link (orelectronic tether) established between a tag 20 and an auxiliary device40. Each auxiliary device 40 can be positioned such that it can receiveinformation from a tag 20 via the RF link 45. The auxiliary device 40 isalso positioned in range of the HMU. This allows the HMU receiver toreceive the reply message (from the auxiliary device to the tag) evenwhen the tag is out of range. Receipt of the reply from the auxiliarydevice in effect allows the HMU to determine that the tag is within anacceptable range. The auxiliary device will only be treated as a validsource if it is previously assigned to the HMU and is not in a currentalarm status.

VI—RF Network Contention—RF Frequency Allocation

In the scenarios discussed above, the RF link 45 is utilized forcommunication between various devices. In certain scenarios, severaldevices may be utilized in relatively close proximity. These devices mayultimately be in contention for use of the RF link. That is two or moredevices may try to communicate via the RF link simultaneously.Accordingly, the RF link can be implemented to eliminate or reducecontention issues. For example, the RF link can be implemented with aplurality of frequencies that are allocated to various devices. Inanother example, the RF link can be implemented with a time slotallocation for each device. Such time slots can be assigned on a fixedor dynamic basis.

In the example shown in Table 1 below, the RF link 45 is implementedwith four frequencies.

Frequency No. Associated Device Description 1 HMU Dynamic Time SlotAllocation 2 Auxiliary Device Frequency Allocation 3 Auxiliary DeviceFrequency Allocation 4 Auxiliary Device Frequency Allocation

In this example, frequency number 1 is utilized for communicationbetween a tag and an HMU. The frequency band is divided into a pluralityof time slots, each of which can be assigned to a specific tag. Timeslot allocation can be performed on a fixed or dynamic basis. In thecase of fixed time slot allocation, the given time slot can be directlyprogrammed into the specific tag as well as the associated HMU prior toany communication taking place. In the case of dynamic time slotallocation, the tag and HMU can conduct initial communications (e.g.,utilizing a pre-selected time slot) before a specific time slot isassigned to a specific tag.

In this example, frequencies 2-4 are generally utilized by a tag tocommunicate with an auxiliary device. In normal operation tag willintermittently or periodically request the presence of an auxiliarydevice by sending out a RF transmission (“ping”) and waiting for a replyfrom any auxiliary device in range via the RF link. Each ping can betransmitted on a different frequency (2-4) until communication betweenthe tag and the auxiliary device is established. Specific frequency canbe selected on specific pattern or random frequency assignment.

VII—Wireless Link—Range Adjustment

In certain scenarios, it may be desirable to adjust the range of thewireless (RF) link 45. For example, the default communication rangebetween a tag 20 and an auxiliary device 40 or HMU 300, 300′ may extendinto unintended areas such as adjoining property. Accordingly, thereceiver in the auxiliary device 40 or HMU 300, 300′ may include thecapability to provide Received Signal Strength Indication measurements(RSSI).

It is generally understood that RSSI measurements denote the receivedradio signal strength. These measurements can be utilized in connectionwith a variety of system functions. For example, RSSI can be usedinternally in a wireless networking card to determine when the amount ofradio energy in the channel is below a certain threshold at which pointthe network card is clear to send (CTS). RSSI can be measured in the IFstage before the IF amplifier. In zero-IF systems, it can be done in thebaseband signal chain, before the baseband amplifier. RSSI measurementscan be output as a DC analog level. However, it is beneficial to sampleRSSI measurements with an internal A/D converter so that resultingnumeric codes available directly to the internal processor 202 (FIG. 3).In the example below, typical RSSI measurements range from about 250(noise level) to about 650 maximum.

In the context herein, RSSI is utilized to determine the relativeproximity or range of the tag 20 to an auxiliary device 40 or HMU 300,300′. This can be accomplished by selecting a pre determined RSSI valueto set the acceptable range of the RF link 45 (i.e., the RSSI mustremain above the pre-determined RSSI level to be considered withinrange). In the alternative, a calibration routine can be utilized. Forexample, the tag can be placed into a range calibration mode in which itpings every few seconds. The tag can then be moved throughout thedesired location during which the auxiliary device 40 or HMU 300, 300′records the lowest RSSI measurement. Once the tag has been movedthroughout the entire location at issue, the calibration process iscomplete and the lowest RSSI measured from the calibration process isused to set the range of the RF link 45. The system can optionallyinclude an acceptable offset range for the RSSI measurement (e.g., userselectable) to account for environmental conditions. In this example, atypical default level for the offset range is 50. It is understood thata variety of antenna types (e.g., omnidirectional, directional . . . )having various characteristics (gain, impedance, directionality,radiation efficiency and the like) can be utilized in combination withthe RSSI based range adjustment discussed above to provide optimalcoverage in a given scenario.

VIII—Exclusion Zone Operation—Sex Offender Context

As discussed above in section IV, the auxiliary device can be utilizedto establish an exclusion zone. This particular mode can be utilized toprovide protection from monitored individuals. In the context of sexoffender monitoring, the invention is particularly useful. Referring toFIG. 1, the offender is fitted with a tag 20. The tag carries outreporting functions with the CMS 10 as outlined above e.g., via thewireless network 25 or HMU 300 (see FIG. 5). Each individual desiringenhanced protection is provided with an auxiliary device (e.g., showngraphically as 40, 40′, 40″ . . . ). As discussed above, the auxiliarydevice can be integrated into an article of clothing such as shoes,socks, pants, shirts, or jackets. Integration of the auxiliary deviceinto an article of clothing can help minimize the risk that theauxiliary device is misplaced or lost. In the alternative, the auxiliarydevice can be integrated into or attached to a backpack, purse, walletor other convenient portable accessory. It is understood that tamperdetection mechanism 214, buzzer 218 and/or accelerometer 215 can beomitted from auxiliary devices used in this context. This can furtherreduce the size and cost of such auxiliary devices. In this mode ofoperation, the location of the auxiliary devices 40, 40′, 40″ . . . neednot be known to the CMS 10.

Operation of the system in this context would proceed as follows: thetag 20 detects an auxiliary device (i.e., the auxiliary device respondsto the ping). The tag establishes communications with the auxiliarydevice, and reports some or all of the following information to the CMS10: auxiliary device ID, tag ID, status of the tag (low battery andcharging), status of the auxiliary device (motion or power). During thismode the tag 20 will continue with its normal operations and logging butwith the additional details of the auxiliary device ID received and itsstatus. This logging can occur relatively frequently (e.g., every oneminute). During this mode the tag 20 will notify the central monitoringsystem of every auxiliary device heard; the tag 20 does not need to beconfigured with the auxiliary device details. Once the tag 20 reportsthe presence of an auxiliary device in an excluded area, the CMS 10 candetermine whether there is unauthorized or undesirable proximity betweena tag (e.g., associated with a sex offender) and an auxiliary device(associated with a child). It is understood that auxiliary device ID canhave a format that is generally associated with a certain class ofindividual (e.g., child) and/or the auxiliary device ID can includespecific information (e.g., a serial number) that is specificallyassociated with a single individual (e.g., a specific child).

IX—Predictive Crime Scene Correlation for Sex Offenders

When operating in the mode discussed above, the system can also providepredictive correlation for potential offenders such as sex offenders.The CMS 10 contains sufficient information in the database 15 toidentify the individual wearing tag 20 as well as the individuals orclass of individuals carrying auxiliary devices 40, 40′, 40″ . . . .Once the programming in the CMS determines that there is unauthorized orundesirable proximity between a tag and an auxiliary device, the systemcan take one or more actions. For example, the CMS can i) notify localauthorities, ii) notify the appropriate agent or parole office, and/oriii) notify other individuals that can take appropriate action. The CMS10 software can also track trends over time. These trends can be trackedand analyzed to enhance the accuracy of any notification actions. Forexample, the CMS can utilize a threshold in connection with or prior toissuing a notification. Exemplary trends can include i) detection ofauxiliary device ID associated with a child multiple times in the samegeneral lat/long location as a sex offender, and/or ii) detection ofauxiliary device ID associated with a child for more than a specifiedtimer period in the same general lat/long location as a sex offender.The system can also provide notification of these trends to an agent forfurther investigation. This can alert the agent to trends that may nototherwise be apparent (e.g., the offender may be hanging around aschool, bus stop, shopping mall, park or the like).

X—Suggested Uses of Each Mode

1) Inclusion Zone Operation (GPS Power Down)

-   -   To confirm the known location of an individual to the vicinity        of an auxiliary device or auxiliary device when GPS is        unavailable i.e. at home or in a establishment i.e., hostel.    -   To extend the operational life of the tag battery by allowing        the tag to use the auxiliary device in a known location.

2) Report Only Mode—Exclusion Zone Operation

-   -   To allow the auxiliary device to be positioned in areas of        importance and to notify the central monitoring system when a        tag is within range i.e. schools or victims properties.    -   The auxiliary device with an extended battery back-up can be        used in this mode by domestic violence victims or other persons        who may require the device to operate as a mobile device. i.e.        taking a trip to the mall or visiting the doctor. The generation        of alarms (including audible and/or visual alarms) may be added        as desired. This mode can also provide protection for children        in cases where there is unauthorized or undesirable proximity        between the child and a sex offender.

3) HMU Range Expansion

-   -   To allow the auxiliary device to be positioned in such a way        that with the operation of the HMU, a property can be        effectively covered with the placement of auxiliary device to        extend the HMU range.    -   The auxiliary device can be used in a number of modes depending        on parameter settings on the tag and if a Home Monitoring unit        (HMU is present).

While the foregoing description and drawings represent the preferredembodiments of the present invention, it will be understood that variouschanges and modifications may be made without departing from the scopeof the present invention.

1. A location tracking device for use with an auxiliary device, thetracking device comprising: position determining circuitry and firstwireless circuitry that communicates position data representative of thelocation of the tracking device to a remote location, second wirelesscircuitry that communicates with the auxiliary device, and wherein thetracking device has at least two operational modes and wherein thetracking device switches operational modes when communication isestablished between the tracking device and the auxiliary device.
 2. Thetracking device of claim 1 wherein, the, auxiliary device has an ID andwherein the tracking device has a first operational mode, whencommunication is not established with the auxiliary device, wherein theposition determining circuitry is maintained in a normal power state anda second operational mode, when communication is established between thetracking device and the auxiliary device, wherein the second wirelesscircuitry receives the auxiliary device ID from the auxiliary device andthe first wireless circuitry communicates the auxiliary device ID to theremote location.
 3. The tracking device of claim 1 wherein the auxiliarydevice has an ID and wherein the tracking device has a first operationalmode, when communication is not established with the auxiliary device,wherein the position determining circuitry is maintained in a normalpower state and a third operational mode, when communication isestablished between the tracking device and the auxiliary device,wherein the position determining circuitry is placed in a reduced powerstate and wherein the second wireless circuitry receives the auxiliarydevice ID from the auxiliary device and the first wireless circuitrycommunicates the auxiliary device ID to the remote location.
 4. Thetracking device of claim 1 wherein the tracking device includes signalstrength circuitry associated with the second wireless circuitry and thetracking device can determine whether radio energy received by thesecond wireless circuitry is below a predetermined threshold.
 5. Thetracking device of claim 1 wherein the tracking device includes at leastone of time slot allocation circuitry and frequency allocation circuitryand the tracking device minimizes contention for frequencies or timeslots associated with the second wireless circuitry.
 6. The trackingdevice of claim 1 wherein the auxiliary device has an ID and wherein theremote location comprises a monitoring station that communicates withthe tracking device and receives the auxiliary device ID from thetracking device when communication is established between the trackingdevice and the auxiliary device, wherein the monitoring station directsthe tracking device to switch operational modes based on the auxiliarydevice ID.
 7. The tracking device of claim 6 wherein the monitoringstation establishes one of an inclusion zone and an exclusion zone basedon the auxiliary device ID.
 8. A auxiliary device for use with alocation tracking device, the auxiliary device comprising: an auxiliarydevice ID and wireless circuitry that communicates the auxiliary deviceID to the location tracking device wherein the location device hasposition determining circuitry and first wireless circuitry thatcommunicates position data representative of the location of thetracking device to a remote location, second wireless circuitry thatcommunicates with the auxiliary device, and wherein the tracking devicehas at least two operational modes and wherein the tracking deviceswitches operational modes when communication is established between thelocation tracking device and the auxiliary device.
 9. The auxiliarydevice of claim 8 wherein the tracking device has a first operationalmode, when communication is not established with the auxiliary device,wherein the position determining circuitry is maintained in a normalpower state and a second operational mode, when communication isestablished between the tracking device and the auxiliary device,wherein the second wireless circuitry receives the auxiliary device IDfrom the auxiliary device and the first wireless Circuitry communicatesthe auxiliary device ID to the remote location.
 10. The auxiliary deviceof claim 8 wherein the tracking device has a first operational mode,when communication is not established with the auxiliary device, whereinthe position determining circuitry is maintained in a normal power stateand a third operational mode, when communication is established betweenthe tracking device and the auxiliary device, wherein the positiondetermining circuitry is placed in a reduced power state and wherein thesecond wireless circuitry receives the auxiliary device ID from theauxiliary device and the first wireless circuitry communicates the ID tothe remote location.
 11. The auxiliary device of claim 8 wherein theremote location comprises a monitoring station that communicates withthe tracking device and receives the auxiliary device ID from thetracking device when communication is established between the trackingdevice and the auxiliary device, wherein the monitoring station directsthe tracking device to switch operational modes based on the auxiliarydevice ID.
 12. The auxiliary device of claim 11 wherein the monitoringstation establishes one of an inclusion zone and an exclusion zone basedon the auxiliary device ID.
 13. A location tracking system comprising: atracking device having position determining circuitry and first wirelesscircuitry for communicating position data representative of the locationof the device to a remote location and second wireless circuitry, anauxiliary device having wireless circuitry that communicates with thetracking device second wireless circuitry, wherein the tracking devicehas at least two operational modes and wherein the tracking deviceswitches operational modes when communication is established between thelocation tracking device and the auxiliary device.
 14. The system ofclaim 13 wherein the auxiliary device has an ID and wherein the trackingdevice has a first operational mode, when communication is notestablished with the auxiliary device, wherein the position determiningcircuitry is maintained in a normal power state and a second operationalmode, when communication is established between the tracking device andthe auxiliary device, wherein the second wireless circuitry receives theauxiliary device ID from the auxiliary device and the first wirelesscircuitry communicates the auxiliary device ID to the remote location.15. The system of claim 13 wherein the auxiliary device has an ID andwherein the tracking device has a first operational mode, whencommunication is not established with the auxiliary device, wherein theposition determining circuitry is maintained in a normal power state anda third operational mode, when communication is established between thetracking device and the auxiliary device, wherein the positiondetermining circuitry is placed in a reduced power state and wherein thesecond wireless circuitry receives the auxiliary device ID from theauxiliary device and the first wireless circuitry communicates theauxiliary device ID to the remote location.
 16. The system of claim 13further comprising an HMU with third wireless circuitry thatcommunicates with at least one of the auxiliary device wirelesscircuitry and the tracking device second wireless circuitry wherein therange of the HMU is expanded when communication is established betweenthe location tracking device and the auxiliary device.
 18. The system ofclaim 13 wherein the auxiliary device has an ID and wherein the remotelocation comprises a monitoring station that communicates with thetracking device and receives the auxiliary device ID from the trackingdevice when communication is established between the tracking device andthe auxiliary device, wherein the monitoring station directs thetracking device to switch operational modes based on the auxiliarydevice ID.
 19. The system of claim 18 wherein the monitoring stationestablishes one of an inclusion zone and an exclusion zone based on theauxiliary device ID.
 20. The system of claim 18 wherein the monitoringstation performs one of proximity detection and predictive correlationbased on the location of the tracking tag and the auxiliary device ID.21-25. (canceled)